


Princess of Crime

by ForbiddenArchive



Category: Fate/Grand Order
Genre: Corruption, Morality Change, mental changes
Language: English
Status: Completed
Published: 2020-12-20
Updated: 2020-12-20
Packaged: 2021-03-10 19:41:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 5,128
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28202529
Author URL: https://archiveofourown.org/users/ForbiddenArchive/pseuds/ForbiddenArchive
Summary: A budding relationship as Father and Daughter between Da Vinci and Moriarty rubs off on the younger girl a little more than the older man ever could've hoped for.
Kudos: 6





	Princess of Crime

Thanks to the many Servants that populated the halls of Chaldea, the brilliant minds that had to deal with them on a daily basis put together a set of rules that would help anybody, no matter how lesser they were, to properly conduct themselves in their presence. Especially when it came to the ones with a lack of proper morals, who would no doubt try to mess with their mortal bodies. If not outright kill them should they say the wrong thing.

One of these Servants detailed in the rules was the Prince of Crime, James Moriarty. After his stunt in Shinjuku, the Servants that knew him and his quirks offered all of their knowledge to find a way to disarm him. Something that was put into practice during the summer race. Simply calling the older man ‘Papa’ was enough to make his heart win out over his mind, leaving him as an overly doting elder man ready to spoil his sweetheart.

Unfortunately, Moriarty had not only figured his own weakness out after those incidents, but he was planning on turning it into a strength. If the complex at large believed that he was harmless whenever he acted like a parent, then their guard would naturally lower in his presence. As long as he played his part, it would be easy to slowly but surely build a brand new plan. One that Holmes wouldn’t be able to stop until it was far too late, and this time he wouldn’t have to rely on another spirit’s powers to augment his own.

No, this time he had something much simpler in store. A little bird told him about Leonardo Da Vinci’s spare body, the one that looked like a child. It didn’t have the exact same origin nor mindset as the original, who had already grown suspicious of him, which meant that he could whisper sweet nothings into the young girl’s ear. Sooner or later, she’d believe them without a second thought…

The only thing he had to avoid was to fall into the trap of paternal affection…

\---

“Tea, little Lady?”

Moriarty came into the younger Da Vinci’s personal workshop, one that he had helped set up after he managed to wake her from her slumber. The original didn’t know that this place existed, nor did the smaller version know that her older self was still alive. This was a little hideout, just for the two of them. 

“Ah! Thank you, Papa.” The little brunette chimed happily as she held out a well-sculpted teacup with a stylized spider engraved on it, smiling as the older man poured scalding hot tea into it…

He smiled in turn as he put down the teapot on a nearby shelf. “How many sugar cubes today, little Lady?” The moustached mastermind asked as the space between his fingers was filled with cubes of sugar, ready to sweeten up the tea as much as she’d like.

“None, Papa. I can handle it without any sweetness.” Da Vinci chimed as she went in to take a sip… only for the older man to stop her, slowly lowering it back onto its plate. “Papa? What’s the matter?”

Moriarty wagged his finger disapprovingly. “Little Lady, if you drink it like this, you’ll just burn your lips and your tongue at the same time. You should wait for it to cool, then you can drink it and savour the taste.” He reminded her of the dangers of a warm beverage, before slipping in a set of sugar cubes. “And a growing girl like you deserves an added kick of sugar. Once you’re older, you can have it as plain as you’d like.” 

The older man tried to sound responsible and wise, but really, he was just imposing his own tastes on the girl. Despite being a criminal mastermind, he did have a wicked sweet tooth. As a good Papa, he wanted to pass that down to her, even though he had bigger goals to worry about…

His “daughter” listened carefully as he spoke, nodding along as she looked into her cup. “Papa? What do you do around the facility?” She asked very pointedly as he handed her a spoon to stir the sweetened and hot drink, humming a little to herself as she felt the warmth it gave off.

“What I do? A lot of things, my little Lady.” Moriarty explained as he took a seat by her workstation, while pouring himself a bit of tea as well. “Whenever our Master needs a plan that’s diabolical enough to require a criminal mind, I am there to help him out. Of course, that blasted Holmes always ends up preempting me and preventing me from lending my talents, but if he was just gone from my sight…” The older man furrowed his brow as he looked into his own tea, scowling.

Da Vinci noticed his foul scowl as she picked up her cup with both hands, sipping from the tea gently. “Papa’s having trouble with Master… Maybe I could help?” The young brunette chimed as she put down the cup, sliding a bit to the right as she pulled out one of her schematics, studying it briefly before putting pen to paper. Papa needed her, so she was ready to help him out. 

The Prince of Crime stared a bit at the younger genius, surprised that she was working with him this early. Well, maybe he had underestimated how much he had managed to nurture her already, and her desire to help him was born from the kindness that he gave her. He’d be lying if he said it didn’t feel good to be rewarded for doing good, but his wicked soul stopped him from dwelling on it for too long.

“What do you have in mind, little Lady?” Moriarty asked aloud as he took a sip from his cup, watching her sketch away on the oversized sheet of paper. She was drawing so quickly that it was hard to make it all out, but the calm that his tea brought him allowed him to see the finer details as they developed, slowly piecing together the bigger picture. It was connected to his desire to talk to his Master, that much he could tell based on those lines...

Once she finished sketching, she moved to the side to allow her Papa to read the schematic properly. He was right that it had to do with communicating, but he didn’t realize just how overboard she’d go. “Well, you said that Mr. Holmes wouldn’t let you talk to the Master if he knew you had something bad in mind, so why do you need to talk to Master in the first place when you can just send your thoughts on the matter straight to his head?” She explained as she pointed towards the sketched device, smiling and beaming with pride. “I can construct a bug that you can plant on Master, which will let you transmit your voice straight into his head regardless of where in the complex he is. If I fine tune it enough, you might even be able to communicate with him whenever he’s in a part of Humanity’s distorted history. It can even function as a secure channel, if he needs to call on your help!” The features sounded extensive, and the big smile on her face showed just how proud she was of it.

To say that the older man was surprised at how much she had thought this little device through would be an understatement. “Oh my.” He muttered under his breath as he took another sip from his cup, before putting it down and kneeling so that he was at eye-level with the young brunette. “You’ve thought hard about this, little Lady. Papa’s proud of you.” He said with a gentle tone, running his hand through her hair as he patted her head.

Da Vinci smiled from ear to ear, happy to be praised as she wrapped her arms around the older man. “Thank you, Papa! I’m so glad you like it!” She chimed, giggling childishly as she was happy to get praise. She didn’t get too much of it, at least not like this, so it was a new sensation that she could cherish from the bottom of her heart.

Moriarty smiled back, resisting the urge to grab her and hug her and praise her even more. The sight of such a young lass being the cutest and proudest that she could be was hurting his elderly heart even more than it normally should. But he had to stay focused, his plan had to succeed. If she could make a device like this, there was no telling what else she could make that would further his plans.

“Little Lady, do you think you could start working on this device today? I have a bad feeling about the next few missions that our dear Master has to go on, and I want to make sure that I can support him from the background.” He asked, pausing before adding a little incentive to the young lady. “If you manage to finish it before tomorrow night, we’ll have all the ice cream that you can eat. For a whole week. How’s that?”

The younger girl’s eyes flashed with hunger as she turned towards the parchment she had drawn her schematic on, nodding rapidly. “I’ll get it done, Papa! You better keep your end of this deal, or I’m gonna tell on Master!” She chimed happily, though knowing her that threat was just as real as her ability to tinker with anything.

Moriarty closed his eyes as he reached for his wallet, feeling a sense of dread overwhelm him. “Y-Yes, of course.” He muttered under his breath as he slowly made his way out of the workshop. Not only did he need to give his dear ‘daughter’ enough space to finish her device, but he had to devise some way to get out of his end of the deal. That, or get the funds he needed to satiate her…

Being a Papa was difficult when your ‘daughter’ was this sweet…

\---

Da Vinci worked her butt off during the entire day, wanting to make the best little device that her Papa could’ve wished for. She made sure that it could do everything she had told him, and then some. In fact, she made two sets, one for the Master and one for him. The one for him was a bit different, and she couldn’t help but giggle a little maniacally as she palmed the device.

This one was designed to help his plans more directly. Instead of allowing him to communicate with their Master, this one would help him listen in on any conversation as long as he reached the proper frequency. With this, he could figure out what everyone else in the complex was doing, when they were doing it, and how he could avoid that annoying detective…

She blinked for a few seconds as the thought of Mr. Holmes crossed her mind. Why did she consider him annoying? The few times she had met him, he was nothing but nice to her. But since Papa considered him annoying, was he really that bad? 

Da Vinci rubbed away at her head, feeling a few of her thoughts scrambling the more she tinkered with the device that she had started making for her Papa. She yawned as she leaned back in her chair, grabbing the spider-patterned cup and taking a small sip from it once more. The tea was cold at this point, but by god it was sweet. 

They did say that revenge was to be served cold. And Papa had a lot of revenge to bring to certain people, especially that annoying detective… So, if the tea in her cup was revenge, did that mean that he considered her an essential part of her plans? And if that was the case, were the devices that she was busy making really meant for any kind of good?

“What am I even doing…” The young genius muttered to herself as she rubbed her eyes, looking down at the two bug-sized pieces of tech, eyeing them with a bit of worry in her eyes. Was this really the way to go about things? Papa was a wonderful man that helped her so much, treated her like she was his daughter and everything… But that didn’t mean that she had to go out of her way to do evil. Right?

Her inner morals were at an impasse with the kind feelings that her dear Papa had shown her, and it was causing her more than a few problems. Maybe if she just focused on finishing the two devices, she could rest easy. He did promise her that he was going to get her ice cream for a week, and that was enough to make both sides of her mind quiet down. The deliciousness of that dessert would help her focus on future projects, and it meant more fun time with Papa, where he didn’t plan on doing anything bad…

Da Vinci kept on tinkering and tinkering, eventually dropping her tools as she yawned. She had finished both the Thought-Transmitter and the Conversation-Receiver. Both of which were ready to be used as soon as Papa needed them. But there was something in the back of her mind, the part that was loyal to the man that had woken her up and treated her like his own daughter, that told her that she wasn’t quite done.

She still needed to show him how much she appreciated him. Making one more device that would help cover his tracks would serve that purpose. But how could he effectively cover his tracks outside of gimmicks that let him escape?

The young girl wracked her brain for a bit as she stared at her parchment, tapping her pen rapidly against it as the thoughts bounced around in her head. How? How would Papa be able to subdue anybody that saw him or happened to be against his plans? What could she possibly make to help him…

Da Vinci’s eyes fluttered as she yawned once more. It was getting really late, and she had hit a mental roadblock. Maybe she should just go to bed and wait for Papa to arrive the next day. He’d know exactly what she should make… He… He’d know, wouldn’t he?

It all clicked as she looked at her cup, and specifically the spider engraved on the side. Of course. How did she miss that crucial detail? She knew exactly what she could do to help him, exactly what device would help him tie up loose ends and keep anybody out of his deceitful web… or rather, pull them in and turn them into a piece of his deceit.

She just needed to make a device that could wrap up the witness and make them a tool of his, like everyone else he had in his web. Like her. Yes, that was it, she needed to make something that embodied her true abilities. Something that only he could use…

Da Vinci’s smile turned a little wicked as she tinkered with her final device throughout the night, happy to please her Papa…

\---

As soon as Morning struck outside the complex, it was time for Moriarty to check in on his little Lady. Something that he frankly dreaded as he wasn’t prepared to get her all the ice cream that she had asked for, and he knew how cranky and bratty she could be when she didn’t get her way. Something that she had taught him on the first day that he took care of her, and the bruises that he still had to show for it.

“You can do this, James. She’s just a kid. Sweet talk her, act like her Papa, and you’ll be fine.” The older man muttered under his breath as he approached her workshop in the basement, taking a deep breath once he stood right in front of the door leading inside. He knew that he could handle her, he just needed to take it slow and make sure that she didn’t get suspicious.

Before he opened the door to her workshop, however, he heard the faint sound of snoring coming from within. Was she still asleep?... Had she even slept throughout the night was the better question, actually, and the answer was most likely a resounding ‘No’. It seemed like she had inherited the workaholic nature of her original self. All to his benefit, of course…

Moriarty carefully stepped inside his ‘daughter’s workshop, making sure to take light steps as to avoid waking up the youth too abruptly. He knew the value of a good night’s sleep, and he certainly hadn’t gotten it either. Worrying about how he was going to pay her back or subvert her desire for all of that ice cream had done that to him, but he at least managed to wake up at the right time…

Once he made it into the center of the workshop, he saw the young inventor laying with her head on the workstation, snoring away with three distinct looking devices laid out in front of her head. One looked like the bug that she had described to him, the other looked similar but had an obvious earpiece making it clear that he had to use it himself, and the last…

The last was a watch that didn’t have any hands on the inside. Instead of a proper set of hands, the midsection of the face was replaced with a rather stylized and carefully crafted spider, almost like the one on the cup that he had gifted her. Which meant that out of the kindness of the little girl’s heart, she had made a device that symbolized him. 

He was touched, frankly. He even teared up a little, proud of the little Lady’s devotion towards him. He had raised her well, and he really could consider her his daughter in every sense of the word. If he could, he’d wake her up and thank her from the bottom of his twisted heart, but that wouldn’t be right for him to do. She still needed her beauty sleep.

Moriarty composed himself, wiping away the tears with his gloved finger as he picked up the watch, carefully examining it to identify exactly what it was able to do. A gadget would be useless if he didn’t understand how to use it, and upon noticing a couple of hidden holes near the face, as well as the presence of a seam between the spider and the rest of the clock, he would hazard a guess as to what it’s true function was. But to properly understand, he’d need a test subject… And nobody would be willing to help him, nobody that was awake at any rate…

“Nnnn… Papa… Papa proud..?” The drowsy murmurs of a sleepy child left the young girl’s mouth as she slowly fluttered back to the land of the living, yawning loudly as she slowly stretched, a satisfied smile on her tired face. She didn’t even realize that the older man had entered the workshop, much less that he was standing right beside her.

Only as she looked around and rubbed away at her eyes did she look straight up at the criminal mastermind, smiling as if she expected to see him right there. “Morning Papa…” She muttered with a bit of a slur to her words, yawning yet again as she turned towards her devices, giggling to herself with pride…

...Then she made a double take and looked right up at the man she considered a paternal figure. “Papa? Why’re you here?” She realized how weird it was to wake up with him at her side, especially since he hadn’t bothered to wake her up. The brunette yawned once more as she stretched, wiping away that weirded out expression with a pure smile just moments later. “Never mind, Papa! What do you think? Did I do a good job? Did I?” Excitement followed suit as she giggled, his presence knocking all the drowsiness out of her.

“You did a wonderful job, little Lady.” Moriarty replied as he gave her the biggest hug that he could muster without giving in to his own paternal instincts. He even lifted her up and spun her around. “You’ve made this old man so happy that he could jump for joy! That’s what a great job you’ve done, Da Vinci!” He laughed, even addressing her properly by name as he spun around.

Little Da Vinci giggled in turn as she hugged him tightly back, nuzzling her cute cheeks into his chest. “Thanks, Papa! I knew you’d love it! I wanted to make sure that you were happy, so I made extra trinkets just so you’d have so much to choose from! Just for you, because you’re the best Papa in the whole wide world!” She chimed, her happiness pouring out from the depths of her heart. Any worry left in there completely crushed by the smile on her old man’s face…

He finally put her back down on the chair as he examined the watch once more, still keeping that smile on his elderly face. “I really have to thank you so much, little Lady. Without you, I wouldn’t be able to carry out my schemes anywhere near as effectively. I’m sure our Master will be very pleased with the help I bring him too, especially since that blasted Holmes won’t be able to stop me ever again.” He monologued, before clearing his throat ever slgihtly and looked down at her again. “Tell me, what does this watch do, exactly? I do adore the effort you went through to replicate my insignia, but it can’t exactly tell time like this, now can it?”

“Well, I wanted to make a trinket that really felt like something you’d use, Papa, so I designed it to clean up any traces of evidence you might’ve left behind…” She paused, before winking a little wickedly. “By turning any witnesses into sleeper agents for your cause and your plots! They just have to watch the spider spin, which you can activate by pressing the button on top, and then they’ll be spun into your web as cute assistants that’ll be happy to obey your orders and destroy any evidence. Even act as stand-ins for your crimes, so you can throw them away at your leisure!” She explained, her voice sounding just a little evil as she spoke. Did she test it out on herself? It wasn’t easy to tell, since she looked very normal at a glance…

Moriarty spun the watch around, nodding to himself. This was why he saw those holes and the seam between the spider and the rest of the watch. Which meant that not only was what she spoke about a mental effect, but a literal one as well. “Is there any sign that they’ve been turned into my pawns, little Lady? Anything that might tie them back to me?” He asked, his tone turning from paternal to scheming, a sly smirk at the edge of his smile…

“Papa’s a master criminal! Leaving behind any evidence at all would be unfair, so the only that can possibly connect the sleeper agent is the webbing in their eyes, which disappears as they get knocked out so they don’t reveal themselves when they’re not acting on your behalf!” Da Vinci proudly explained, with not a single piece of webbing visible in her eyes. It wasn’t because she had brainwashed herself into being a tool that she worked so hard to bring the older man a trinket that would help him out immensely…

It was because she loved him like a daughter should. “Well, Papa? Is it useful? Did I do good?” She chimed once more, wanting more of the praise that she had grown addicted to. She had worked so hard for it, she wanted nothing more…

Unfortunately, as she opened her eyes to look up at him, she instead found them drawn to a spinning spider right in front of her face. Almost instantly, her own eyes, still tired from the lack of proper sleep, started spinning in repeated circles… “P-Pa… papa…” She muttered, feeling hurt over what felt like a betrayal.

“Ssssh. It’ll be okay, little Lady. I don’t plan on making you into any kind of pawn, much less a disposable tool. You’re my daughter, after all.” Moriarty explained as he carefully ran his hand through her hair, petting her with a soft smile on his elderly face. “I just want to strength the bond between us. There may not be blood connecting us, but I will show you the truth of the crimes I commit, and I trust you to join me as my little Princess of Crime, putting your talents to good use for my schemes. You can do that for your dear Papa, can’t you, Da Vinci?”

As the spider on the watch spun, the holes on the sides opened up ever so slightly and shot out a series of glowing webbing, no doubt crafted from very finely-controlled mana. It wrapped around the entranced girl’s head, spreading across her body as it weaved itself into a full and proper cocoon. All while leaving her eyes exposed so that the trance wouldn’t be broken. She just kept on watching that beautiful and malicious spider spin around…

Her dear Papa just stood there, keeping the watch active for as long as it needed to. The thicker the cocoon, the deeper and irreversible the transformation would be. He figured that if it could make sleeper agents, then it could truly transform somebody into an evil soul if it was used for a prolonged period of time. Combine that with a little push from one of his own skills to impart the [Evil] alignment on her, and the little genius would soon become his daughter in every sense of the word. 

Da Vinci’s mind was wrapped up by the mana threads that ran along her body. All of her thoughts were webbed up, stored away for safekeeping, preventing her from thinking on her own. New thoughts instead spun inside her mind, ones that all revolved around her dear Papa. James Moriarty, the Prince of Crime, the one she should serve with all of her heart. 

At least, that’s what the watch was supposed to do… but because of her Papa’s love, and the love she held for him, that undivided love was altered in just the right way. Instead of devotion towards him as a master, that daughterly love grew and grew, until it was visible in her eyes in the form of two webbed up hearts taking the place of her irises. Hearts filled with true cruelty and deviancy like her dear Papa’s…

Once Moriarty saw the change in her eyes, he knew that the watch had done everything it needed to. He let go of the button and held it by its chain instead, carefully dropping it into his shirt’s pocket before looking down at the girl one more time, eagerly smiling as the cocoon came undone. His daughter was about to be reborn, and he wouldn’t want to miss it.

The silken strings that held the genius girl captive slowly came undone. Or rather, they were sucked into her body as it became visible, with most of her former attire having been resown while she was stuck. Instead of the calm and comforting browns, blues and reds, only a foreboding and menacing black remained. It reached from her neck all the way down to her thighs, leaving just enough of her legs exposed before they were covered in a similarly black pair of stockings. Her heels, beautifully split between black and white, clacked against the floor as she stood up tall with an awful smile on her face.

Da Vinci grabbed ahold of her skirt and gently curtsied, with webbing flying out from underneath the short cloth as it then clung to her clothing. Her black dress was covered in a silky pattern of white and purple, her leggings gained a web-like texture to them, and the gloves that she wore to protect her delicate fingers, which now reached all the way up to her elbows like a mature lady’s gloves would, gained that very same texture. All a symbol of how she had been wrapped up in her Papa’s schemes, and how she was just as much of a schemer as he was, when it came down to it.

Finally, her eyes weren’t the only thing that had changed about her face. Her skintone had paled ever slightly making her look a ghastly white, which was nicely complemented with string-like markings that reached around her eyes, making both of her heart-irises seem like the center of their own webs. Combine that with another set of web-markings on her cheeks that were decorated with stylized spiders in the middle, and she looked… well, ridiculous, but she was a villain, and more importantly, the daughter of the Prince of Crime! He had his own taste for extravagant schemes, and she had her tastes for extravagant fashion! As a real daughter should!

“Papa!” She cried out with joy as her wicked smile filled her expression. “What kind of schemes are we going to cook up today? Are we going to finally deal with that bastard Holmes? Are we going to steal away Master’s rights? Are we going to steal a couple of hearts? What are we going to do?” She sounded gleeful as she suggested many villainous actions, giggling without a shred of her former good or innocence left in her voice.

Moriarty laughed along with her as he picked her up, giving her a brief kiss on that spider-laden cheek. “Right now, we’re going to plan, my little Princess. Then, and only then, can we pull off the heist of a lifetime!” He declared as he spun around with her in his arms once more, delight filling his old and decrepit heart. “Ah, Da Vinci! You’re the daughter I always wished I had!”

“And you’re the best Papa a daughter could ever wish for, the worst villain of them all!” Da Vinci laughed along with her beloved Papa, fully immersing herself in the role as the Princess of Crime. She’d make all of his gadgets and even a few of her own, and he’d carry out all of his new plans without a hitch. Together, they were the perfect team, the perfect Father and Daughter pair!

Chaldea would soon come to fear the Prince and Princess of Crime, as their schemes took the complex by storm...


End file.
